[转载代码] [PowerShell每日技巧]添加、删除环境变量(20140207)

DAIC

PowerShell can read environment variables easily. This returns the current windows folder:

$env:windir
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However, if you want to make permanent changes to user or machine environment variables, you need to access .NET functionality. Here is a simple function that makes setting or deleting environment variables a snap:

function Set-EnvironmentVariable
{
    param
    (
        [Parameter(Mandatory=$true, HelpMessage='Help note')]
        $Name,

        [System.EnvironmentVariableTarget]
        $Target,

        $Value = $null

    )

    [System.Environment]::SetEnvironmentVariable($Name, $Value, $Target )

}
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To create a permanent user environment variable, try this:

Set-EnvironmentVariable -Name TestVar -Value 123 -Target User
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Note that new user variables are visible only to newly launched applications. Applications that were already running will keep their copied process set unless they explicitly ask for changed variables.

And here is the line that deletes the variable again:

Set-EnvironmentVariable -Name TestVar -Value '' -Target User
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http://powershell.com/cs/blogs/tips/archive/2014/02/07/setting-and-deleting-environment-variables.aspx